Thank you for your posts.
We have been faced with this issue, and our developers are looking for a way to solve it.
Actually, when the issue is reproduced, the search window appears, however, it is hidden behind a screen - this is known issue from Visual Studio Isolated Shell 2013. Since the IDE is based on it, this requires additional investigations to solve it in The Welkin Suite.
If you would be faced with this again, please restart the IDE.
Also, as the additional workaround to avoid this issue until we will fix it, you can pin the 'Find and Replace' window in TWS UI as a separate panel - in this case, it always will appear and will be visible for you.